scholarly journals Broad-lined type Ic supernova iPTF16asu: A challenge to all popular models

2019 ◽  
Vol 489 (1) ◽  
pp. 1110-1119 ◽  
Author(s):  
L J Wang ◽  
X F Wang ◽  
Z Cano ◽  
S Q Wang ◽  
L D Liu ◽  
...  
Keyword(s):  
Light Curve ◽  
Rest Frame ◽  
Mass Loss Rate ◽  
Natural Extension ◽  
Late Time ◽  
Rapid Rise ◽  
Model Interaction ◽  
Cascade Decay ◽  
Radioactive Heating ◽  
Very High

ABSTRACT It is well known that ordinary supernovae (SNe) are powered by 56Ni cascade decay. Broad-lined type Ic SNe (SNe Ic-BL) are a subclass of SNe that are not all exclusively powered by 56Ni decay. It was suggested that some SNe Ic-BL are powered by magnetar spin-down. iPTF16asu is a peculiar broad-lined type Ic supernova discovered by the intermediate Palomar Transient Factory. With a rest-frame rise time of only 4 d, iPTF16asu challenges the existing popular models, for example, the radioactive heating (56Ni-only) and the magnetar +56Ni models. Here we show that this rapid rise could be attributed to interaction between the SN ejecta and a pre-existing circumstellar medium ejected by the progenitor during its final stages of evolution, while the late-time light curve can be better explained by energy input from a rapidly spinning magnetar. This model is a natural extension to the previous magnetar model. The mass-loss rate of the progenitor and ejecta mass are consistent with a progenitor that experienced a common envelope evolution in a binary. An alternative model for the early rapid rise of the light curve is the cooling of a shock propagating into an extended envelope of the progenitor. It is difficult at this stage to tell which model (interaction+magnetar + 56Ni or cooling+magnetar + 56Ni) is better for iPTF16asu. However, it is worth noting that the inferred envelope mass in the cooling+magnetar + 56Ni is very high.

scholarly journals Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light-curve flattening

2020 ◽  
Vol 493 (4) ◽  
pp. 5617-5624
Author(s):  
Doron Kushnir ◽  
Eli Waxman
Keyword(s):  
Light Curve ◽  
Weighted Average ◽  
Far Infrared ◽  
Average Density ◽  
Light Curves ◽  
Type Ia Supernovae ◽  
Late Time ◽  
Simple Method ◽  
Type Ia ◽  
Ia Supernovae

ABSTRACT The finite time, τdep, over which positrons from β+ decays of 56Co deposit energy in type Ia supernovae ejecta lead, in case the positrons are trapped, to a slower decay of the bolometric luminosity compared to an exponential decline. Significant light-curve flattening is obtained when the ejecta density drops below the value for which τdep equals the 56Co lifetime. We provide a simple method to accurately describe this ‘delayed deposition’ effect, which is straightforward to use for analysis of observed light curves. We find that the ejecta heating is dominated by delayed deposition typically from 600 to 1200 d, and only later by longer lived isotopes 57Co and 55Fe decay (assuming solar abundance). For the relatively narrow 56Ni velocity distributions of commonly studied explosion models, the modification of the light curve depends mainly on the 56Ni mass-weighted average density, 〈ρ〉t3. Accurate late-time bolometric light curves, which may be obtained with JWST far-infrared (far-IR) measurements, will thus enable to discriminate between explosion models by determining 〈ρ〉t3 (and the 57Co and 55Fe abundances). The flattening of light curves inferred from recent observations, which is uncertain due to the lack of far-IR data, is readily explained by delayed deposition in models with $\langle \rho \rangle t^{3} \approx 0.2\, \mathrm{M}_{\odot }\, (10^{4}\, \textrm{km}\, \textrm{s}^{-1})^{-3}$, and does not imply supersolar 57Co and 55Fe abundances.

scholarly journals Observations of the low-luminosity Type Iax supernova 2019gsc: a fainter clone of SN 2008ha?

2020 ◽  
Vol 496 (2) ◽  
pp. 1132-1143 ◽  
Author(s):  
Lina Tomasella ◽  
Maximilian Stritzinger ◽  
Stefano Benetti ◽  
Nancy Elias-Rosa ◽  
Enrico Cappellaro ◽  
...  
Keyword(s):  
Light Curve ◽  
Host Galaxy ◽  
Late Time ◽  
Spectral Features ◽  
Data Set ◽  
Oxygen Abundance ◽  
Band Maximum ◽  
Photometric And Spectroscopic Observations ◽  
Decline Rate ◽  
Peak Luminosity

ABSTRACT We present optical photometric and spectroscopic observations of the faint-and-fast evolving Type Iax supernova (SN) 2019gsc, extending from the time of g-band maximum until about 50 d post-maximum, when the object faded to an apparent r-band magnitude mr = 22.48 ± 0.11 mag. SN 2019gsc reached a peak luminosity of only Mg = −13.58 ± 0.15 mag, and is characterized with a post-maximum decline rate Δm15(g) = 1.08 ± 0.14 mag. These light curve parameters are comparable to those measured for SN 2008ha of Mg = −13.89 ± 0.14 mag at peak and Δm15(g) =1.80 ± 0.03 mag. The spectral features of SN 2019gsc also resemble those of SN 2008ha at similar phases. This includes both the extremely low ejecta velocity at maximum, ∼3000 km s−1, and at late-time (phase +54 d) strong forbidden iron and cobalt lines as well as both forbidden and permitted calcium features. Furthermore, akin to SN 2008ha, the bolometric light curve of SN 2019gsc is consistent with the production of ≈0.003 ± 0.001 M⊙ of 56Ni. The explosion parameters, Mej ≈ 0.13 M⊙ and Ek ≈ 12 × 1048 erg, are also similar to those inferred for SN 2008ha. We estimate a subsolar oxygen abundance for the host galaxy of SN 2019gsc (12  + log10(O/H) =8.10 ± 0.18 dex), consistent with the equally metal-poor environment of SN 2008ha. Altogether, our data set for SN 2019gsc indicates that this is a member of a small but growing group of extreme SN Iax that includes SN 2008ha and SN 2010ae.

scholarly journals A type Ia supernova at the heart of superluminous transient SN 2006gy

Science ◽  
2020 ◽  
Vol 367 (6476) ◽  
pp. 415-418 ◽  
Author(s):  
Anders Jerkstrand ◽  
Keiichi Maeda ◽  
Koji S. Kawabata
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Supernova Explosion ◽  
Large Mass ◽  
Late Time ◽  
Standard Type ◽  
Circumstellar Material ◽  
Common Envelope ◽  
Type Ia Supernova ◽  
Type Ia

Superluminous supernovae radiate up to 100 times more energy than normal supernovae. The origin of this energy and the nature of the stellar progenitors of these transients are poorly understood. We identify neutral iron lines in the spectrum of one such supernova, SN 2006gy, and show that they require a large mass of iron (≳0.3 solar masses) expanding at 1500 kilometers per second. By modeling a standard type Ia supernova hitting a shell of circumstellar material, we produce a light curve and late-time iron-dominated spectrum that match the observations of SN 2006gy. In such a scenario, common envelope evolution of a progenitor binary system can synchronize envelope ejection and supernova explosion and may explain these bright transients.

Very high energy y-rays from Cygnus X-3

1981 ◽  
Vol 301 (1462) ◽  
pp. 633-634 ◽  
Keyword(s):  
Light Curve ◽  
High Energy ◽  
Crimean Astrophysical Observatory ◽  
Sharp Peak ◽  
X Rays ◽  
Very High Energy ◽  
Time Variations ◽  
Comparison Of The Results ◽  
Very High

Very high energy y-rays (above 10 12 eV) from Cyg X-3 have been observed for 7 years at the Crimean Astrophysical Observatory by means of the Cherenkov technique. These observations enable us to find the derivative with time of the 4.8 hour periodicity. As is well known, the observations of X -rays have revealed time variations of the Cyg X-3 period (see, for instance, Eisner et al. 1979). The ‘light’ curve for very high energy y-rays has a sharp peak lasting 15 minutes and differs significantly from the ‘light’ curve for X-rays. For this reason the comparison of the results in these two regions is important.

scholarly journals LSQ13ddu: a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures

2020 ◽  
Vol 492 (2) ◽  
pp. 2208-2228 ◽  
Author(s):  
Peter Clark ◽  
Kate Maguire ◽  
Cosimo Inserra ◽  
Simon Prentice ◽  
Stephen J Smartt ◽  
...  
Keyword(s):  
Light Curve ◽  
Time Behaviour ◽  
Rapid Rise ◽  
Circumstellar Material ◽  
Luminous Blue Variables ◽  
Decay Component ◽  
Wind Velocities

ABSTRACT This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 ± 0.9 d to reach a peak brightness of −19.70 ± 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow $\mathrm{ He}\, {\small I}$ features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow $\mathrm{ He}\, {\small I}$ velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive 56Ni powering but can be explained through a combination of CSM interaction and an underlying 56Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib.

scholarly journals WHAT IS THE SUSY MASS SCALE?

2005 ◽  
Vol 14 (11) ◽  
pp. 1907-1917 ◽  
Author(s):  
REUVEN OPHER ◽  
ANA PELINSON
Keyword(s):  
Natural Extension ◽  
Mass Scale ◽  
Density Fluctuations ◽  
Quantum Corrections ◽  
Microwave Background ◽  
Particle Content ◽  
Starobinsky Model ◽  
Cosmological Scenario ◽  
Einstein's Equation ◽  
Very High

The energy, or mass scale M SUSY , of the supersymmetry (SUSY) phase transition is, as yet, unknown. If it is very high (i.e. ≫103 GeV ), terrestrial accelerators will not be able to measure it. We determine M SUSY here by combining theory with the cosmic microwave background (CMB) data. Starobinsky suggested an inflationary cosmological scenario in which inflation is driven by quantum corrections to the vacuum Einstein's equation. The modified Starobinsky model (MSM) is a natural extension of this. In the MSM, the quantum corrections are the quantum fluctuations of the supersymmetric (SUSY) particles, whose particle content creates inflation and whose masses terminate it. Since the MSM is difficult to solve until the end of the inflation period, we assume here that an effective inflaton potential (EIP) that reproduces the time dependence of the cosmological scale factor of the MSM can be used to make predictions for the MSM. We predict the SUSY mass scale to be M SUSY ≃ 1015 GeV , thus satisfying the requirement that the predicted density fluctuations of the MSM is in agreement with the observed CMB data.

scholarly journals Final Moments. I. Precursor Emission, Envelope Inflation, and Enhanced Mass Loss Preceding the Luminous Type II Supernova 2020tlf

2022 ◽  
Vol 924 (1) ◽  
pp. 15
Author(s):  
W. V. Jacobson-Galán ◽  
L. Dessart ◽  
D. O. Jones ◽  
R. Margutti ◽  
D. L. Coppejans ◽  
...  
Keyword(s):  
Light Curve ◽  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Type Ii ◽  
Stellar Envelope ◽  
Circumstellar Material ◽  
Associated Mass ◽  
Flash Spectroscopy

Abstract We present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal Type II-P/L SN with confirmed precursor emission, as detected by the Young Supernova Experiment transient survey. Pre-SN activity was detected in riz-bands at −130 days and persisted at relatively constant flux until first light. Soon after discovery, “flash” spectroscopy of SN 2020tlf revealed narrow, symmetric emission lines that resulted from the photoionization of circumstellar material (CSM) shed in progenitor mass-loss episodes before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a red supergiant (RSG) progenitor with zero-age main-sequence mass of only 10–12 M ⊙, as inferred from nebular spectra. Modeling of the light curve and multi-epoch spectra with the non-LTE radiative-transfer code CMFGEN and radiation-hydrodynamical code HERACLES suggests a dense CSM limited to r ≈ 1015 cm, and mass-loss rate of 10−2 M ⊙ yr−1. The luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with an RSG model with R ⋆ = 1100 R ⊙. Limits on the shock-powered X-ray and radio luminosity are consistent with model conclusions and suggest a CSM density of ρ < 2 × 10−16 g cm−3 for distances from the progenitor star of r ≈ 5 × 1015 cm, as well as a mass-loss rate of M ̇ < 1.3 × 10 − 5 M ☉ yr − 1 at larger distances. A promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion.

scholarly journals Catching a star before explosion: the luminous blue variable progenitor of SN 2015bh

2018 ◽  
Vol 617 ◽  
pp. A115 ◽  
Author(s):  
I. Boian ◽  
J. H. Groh
Keyword(s):  
Loss Rate ◽  
Mass Loss Rate ◽  
Core Collapse ◽  
Late Time ◽  
High Wind ◽  
Hole Formation ◽  
Remarkable Case ◽  
Core Collapse Supernova ◽  
Luminous Blue Variable ◽  
Significant Attention

In this paper we analyse the pre-explosion spectrum of SN2015bh by performing radiative transfer simulations using the CMFGEN code. This object has attracted significant attention due to its remarkable similarity to SN2009ip in both its pre- and post-explosion behaviour. They seem to belong to a class of events for which the fate as a genuine core-collapse supernova or a non-terminal explosion is still under debate. Our CMFGEN models suggest that the progenitor of SN2015bh had an effective temperature between 8700 and 10 000 K, had a luminosity in the range ≃1.8−4.74 × 106 L⊙, contained at least 25% H in mass at the surface, and had half-solar Fe abundances. The results also show that the progenitor of SN2015bh generated an extended wind with a mass-loss rate of ≃6 × 10−4 to 1.5 × 10−3 M⊙ yr−1 and a velocity of 1000km s−1. We determined that the wind extended to at least 2.57 × 1014 cm and lasted for at least 30 days prior to the observations, releasing 5 × 10−5 M⊙ into the circumstellar medium. In analogy to 2009ip, we propose that this is the material that the explosive ejecta could interact at late epochs, perhaps producing observable signatures that can be probed with future observations. We conclude that the progenitor of SN2015bh was most likely a warm luminous blue variable of at least 35 M⊙ before the explosion. Considering the high wind velocity, we cannot exclude the possibility that the progenitor was a Wolf–Rayet (WR) star that inflated just before the 2013 eruption, similar to HD5980 during its 1994 episode. If the star survived, late-time spectroscopy may reveal either a similar luminous blue variable (LBV) or a WR star, depending on the mass of the H envelope before the explosion. If the star exploded as a genuine supernova (SN), 2015bh would be a remarkable case of a successful explosion after black hole formation in a star with a possible minimum mass 35 M⊙ at the pre-SN stage.

scholarly journals Properties of X-ray emission of an aspherical shock breakout

2017 ◽  
Vol 12 (S331) ◽  
pp. 51-56
Author(s):  
Yukari Ohtani ◽  
Akihiro Suzuki ◽  
Toshikazu Shigeyama ◽  
Masaomi Tanaka
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Light Curve ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Circumstellar Matter ◽  
Spherically Symmetric ◽  
Viewing Angle ◽  
Speed Of Light ◽  
X Ray

AbstractWe investigate the relation between the emission properties of supernova shock breakout in the circumstellar matter (CSM) and the behavior of the shock. Using a Monte-Carlo method, we examine how the light curve and spectrum depends on the asphericity of the shock and bulk-Compton scattering, and compare the results with the observed properties of X-ray outburst (XRO) 080109/SN 2008D. We found that the rise and decay time of the X-ray light curve do not significantly depend on the degree of shock asphericity and the viewing angle in a steady and spherically symmetric CSM. The observed X-light curve and spectrum of XRO 080109 can be reproduced by considering the shock with a radial velocity of 60% of the speed of light, and the wind mass loss rate is about 5 × 10−4M⊙.

American Art, “Experts,” and Auction Institutions

2017 ◽  
Author(s):  
Robert B. Ekelund ◽  
John D. Jackson ◽  
Robert D. Tollison
Keyword(s):  
American Art ◽  
Rapid Rise ◽  
Auction House ◽  
Auction Houses ◽  
Profit Maximizing ◽  
American Artists ◽  
Very High ◽  
Art Prices ◽  
Art Experts

Estimates made by “experts” regarding the value of a painting to be offered at auction are evaluated as to whether or not they provide a “fair” or “unbiased” range. Using a sample of eighty American artists over the period 1987–2013, evidence is found that in general art prices are underestimated, but that very high priced art may be overestimated in the interests of profit-maximizing auction houses; we also find that the higher the low estimate, the less likely a painting is to sell, and the wider the range between high and low estimated, the more likely it is to sell; that if a painting does not sell on first offer, its hammer price will be about 60 percent lower if it sells on the next offering (it is “burned”); and that the rapid rise in buyer’s premiums charged by auction houses has had, in combination with other factors, a reduction in auction house revenues.

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